Telephone system



T. F. CROCKER TELEPHONE SYSTEM Sept. 23, 1930.

QWNNSQ Imran m" v asFCruckEr Filed March 14, 1929 AWNEEE a y 33/530 7V31N39 NOEH Patented Sept. 23, 1930 Thomas F.

PATENTAAOFFICE d I 0300x311, or cnroaeo, iLLINoIs, AssIeNoR T RESERVE Honnme coi PANY, OF CHICAGO, ILLINOIS, A CORPORATION 0 DELAWARE TELEPHONE SYSTEM Applieation filed March 14, 1929. Serial No. 346,861.

This invention relates to telephone systems in general, but isconcerned more particularly with trunk circuits and auxiliary equipment for connectin small private automatic telephone exchanges with central ofices of various types.

V The invention is especially adapted for establishing temporary trunk connections between private automatic exchange,hereinafter referred to as a P. A. X., installed on a ship and a central office ashore. Navalve sole, and also ships of the merchant marine, are frequently equipped with a small P. A. X. for providing service between different stais tions aboard ship, suchas the various officers quarters, bridge, engine room, etc. The service provided is necessarily entirely local when the vessel is at sea. 'However, when the vessel is in port it is often desirable to establish a connection between the P. A. X. and a central office of the port, in order that business may betransacted by telephone with various establishments ashore.

Ships, as a rule, will put in at a number of different ports, and it is very probable that in the different ports different types of telephone systems will be in use. In order to meet these conditions to the best advantage, a connecting circuit should have a universal application; that is, it should be capable of being used with any of the types of telephone systems general use, such as magneto and common" battery manualsystems and auto matic systems.

Furthermore, since the call numbers of the PVA. X. stations will usually be unknown to the central oflice subscribers and operators, it

desirable that all calls from the central oflice to the RA. X; be answeredby an attendfor this limited duty. Instead, the duty may be delegated to seaman whose limited trainingmakes it desirable that the routine of an.- swering and completing calls be as simple is practicable.

. One of the main features ofithe invention is the provision of a trunkcircuit for use under the above described conditions which will operatesatisfactorily with any ofthe commonly used types of central office equip' ment. a

Another feature is the extreme simplicity of the attendants equipment and the resultant simplicity of routine operations of answering and extending calls.

Another feature is the arrangement ,for givingthe callingcentral ofiice subscriber or operator a distinctive tone toindicate that the call has been extended tothe P. A. X. This featureinvolves a novel means forgencrating the tone and for impressing iton the trunk in responseto a call a r 1 Another featureis the arrangementwhereby the attendant controls the release of the P. A. X. equipment until the call is answered, whereupon the control istransferredtothe called station: i t 3 V y The foregoing features, together with others not specifically mentioned, will be described in detail with the "aid of the accompanying drawing, which discloses the inventionbymeans of the usual schema-tic circuit diagrams and which shows suflic-ient equipment in a telephone system in which the invention may be employedso that its operation may be readily understood. i

Referring now to the drawing, trunk equipment TR is individual to the trunk and associated therewith is the. common equip ment including night alarm apparatusNA, operators telephone set OTS, and ring-back tone generator RBT. -Line switch LS, also individual to the trunk, is an ordinary rotary I type lineswitch whose wipers move only in. a forward direction and have nonormal or home position. Line switch LS, together with other similar lineswitches of the PLA. X., have access to the regular P. A.'X. connectors such as C, which in turn have access. to the various P, A. X. subscribers linesof which that terminating in substation T is shown. Connector C may be of the samegeneral type as the connector shown in Fig. 2 of United States Patent No. 1,175,119 to A; H. Blessing, issued March 14, 1916.; Substation T is an ordinary automatic substation set comprising the usual talking, signaling, and impulsing instrumentalities.

The operation, briefly stated, is as follows: When a call from the central oliice is extended to the P. A. X. over the trunk, a signal at the atten'dants "position is operated. The ring-back tone apparatus is also operated and places a characteristic tone on the trunk to inform the calling subscriberor operator. that the call hasbeenextended. Upon notingthe signal, the attendant answers by operating key K to the left, thereby establishing a talking connection with the central oiiice subscriber or operator and. disconnecting the ring-back tone equipment. After being 1nformed as to whom the call is'for, the at tenda'nt operates key K to the right and completes a connection to line switch LS in the P. A. X. The line switch further extends the connection to an idle connector such as C. The attendant then dials the number of the .wanted PI A. X. station. The connector signals the wanted station in the usual manner and when the called statlon answers reverses battery back over the. callingtrunk. After dialing, the attendant restores key K to normal or may operate the'key to'the left to listen in on the trunk. The attendant'must not hang up the receiver until the called station answers. When the connector reverses, battery, an additionallocking circuit for the trunk equipmentiis completed, thereby placing Control of the release wit-hthe'c'alled'stw tion. When the attendant is assured that the call has been answered, the attendants receiver may be replaced or other calls may be handled. When the called station disconnects, thelocking circuit, for the trunk equipment is opened and the equipment releasesl 4o" 'Havingbriefiy described the operation and the apparatus involved, a, detailed description of the operation will now be given.- It will be assumed that a call is'extended to the P. A. X. from a common battery manualcentral ofiice. When the operator plugs in, a circuit is completed by way of the operators cord circuit (not shown), conductor. f the trunk, upper left-hand winding of repeating coil R, upper winding of relay 11', condenser 4, lower left-hand Winding of repeating coil R, conductor 3, back tothe operators cord relay 31 also closes a circuit from battery by way of armature 34 and its working contact to the night key which, however, is operated only when the attendant is absent from the position; the night key being normal, no action takes place. If the night key is operated, thebuzzer will audibly signal. the attendant.

Relay 51 also operates in series with relays 11 and 31 and at armature 56. completes acircuit for relay 52 including resistance 61. Relay 52 operates and at armature 57 closes a circuit for relay 53. Relay 53 is of the same general type as the relay shown in Fig. 1 of United; States Patent No. 1,641,256 to J. Erickson, issued September 6, 1927. When its circuit is closed, relay 53 actuates its armature 58'. Spring 64 is rigidly fixed at its upper end 65 and at its lower end is fitted with a weight 63. At the point between the fixed end and the weight is a small projection or contact 66' with which a corresponding contact on armature 58' engages when relay 53 is energized. The engagemento'f the two contacts starts spring 64 to vibrating as a pendulum with the axis at the fixed'end 65. As armature 58 remains in actuated position, it tends to damp the vibrations of spring 64. The amplitude'ofthe vi brations gradually decreases and the frequency gradually increases, the change in frequency being more marked as the ampli'- tude approaches zero. The contacts between the armature and the spring remain closed for gradually increasing intervals with each cycle of vibrations.

The closure of the vibrating contacts completes a circuit for slow-acting relay 54. This relay has a high impedance and when its'circuit is closed for very short intervals doesnot actuate its armature. 1V hen the closed circuit" interval increases sufiiciently, the relay energizes and maintains its armature in oper' ated position for the remainderof the period of vibration of spring 64. At armature 59, the tone lead is connected to a point between therelay'and the vibrating contacts and the remainder of the vibrations serve to produce a tone therein. These vibrations persist for a short time after relay 54 has operated and the tone produced is transmitted back by way of armature 59, condenser 55', armature 14', lower winding of relay 11 to battery.

Relay 54 also short circuits the winding of relay 52 at armature 60. Relay 52 which is also slow acting deenergizes aftera short interval and opens the circuit of relay 53 which also deenergizes. The denergization of relay 53 separates the vibrating contacts 66, thereby stopping the tone (assuming that the vibrations persist until relay 52 deenergizes) and also openingthe circuit of relay 54. Relay 54 deenergizes, opens a point in the tone c1rcuit at armature 59, and also removes the short circuit from relay 52. Relay 52 again v, starts .t-he cycle of operations ete v as previously descrite as long as relay 51 re nains'e fg zl Y A s prevlously stated, the pp d lower windings jo f relay "11 are; inductively coupled. The tone current flowing periodically in the lower winding is induced in the peating coil R, The operation of'keyK also" places a short circuit around condenser 4 and relaylll and around condenser 5, which closes a direct current, path over trunk conductors to "vef the (operator answering supervision and? prove the transmission, and also opens the circiiit of the lowerj'winding, of relay 11 and 'the ring-back tone equipment." Relays 11,31,,and ldeenergize thereby stoppingthe operation of the ring' b'ack tone'apparatus and ezttin'guishing lamp The attendant; then mnverseswitu the cent-raloffiee operator or subscriber to determine the wanted party at the 'P{ A], It willbe noted that in removing'the reeei'ver from the hook acircuitwas closed fromthe' ground by way of the s'witclia hook, transmitter, right hand winding of induction' coil lCywindin'g ofrelay 32 to tat; tery-i 'Relay32"'operates and at armature closes a circuit to the trunk equipment, the

utility of which"*will be described later on. fjA fter ascertaining the number or the name of the 'P. A. Xlsubsc'riber wanted, the at t'end'ant operates lrey K tothe right, thereby 1 closing an obvious c'ircuit for the lower winding of' relay1 3, disconnecting "the talking leads fromthe repeating coiland closing a circuit 'fOrcaIIing'de'ViCte CDI Relay 13 opcrates andat armature18 closes a locking circult for its lower winding, including armature 35 of relay 32-. At armature 19 a circuit is closed for the upper winding of pola rized relay- 12, which does not' operatef however,

' 74'and' its'restingcontact, armature 16, upper overits upper winding alonel At armatures 16'and 20 calling device CD is bridged across the trunk conductors leading to'lineswitch LS, the circuit of which may be traced asfollows battery, winding ofrelay 72, armature right-hand operated contact of key K, contacts ofcalling device CD, lowerright-h'and operated contact of key K, armature 20, armature 76 and its resting contact to ground.

Relay72operates over the above-traced cir{ cult and at iarina'ture77 completes a circuit for relay 71 andmotor magnet 73 in'series and at armature 78 connects test wiper 8-1 to the junction of relay 71 and the motor magnet. In case the Wipers of the line switch are standing on a busy trunk,,wiper 81 will find a ground, Anoperating circuit for the rotary magnet may be traced from' ground, wiper 81, armature and its resting contact, armature 78, interrupter springs, winding of rotary magnet 7 3 to battery. Rotary magnet 73, on operating, opens its own circuit at the interrupter springs and on deenergizing steps the wipers ahead to the next set of contacts. This cycle of operation is repeated as long as wiper 81 encounters a grounded con-. tact. Relay 71 is prevented from operating at this time, being shunted out by the ground on the test wiper. When an idle contact is found, wiper 81 will not encounter a ground, and relay 71 will,' therefore, operate 'over the previously traced circuit including the wind ing of rotary magnet 73. The rotary magwhen the connector returns a ground-over in operated position. v a

Relay 71 also disconnects relay 72 from the trunk, and this relay, being slow acting, will maintain its armatures in operated. position for a short time thereafter, providing a hold-- ing ground for relay 71 until the connector has had time to return the holding groundover the test wiper. The attendant now dials the digits of the called-P. A. X. station, oper-' ating connector in the usual way to step its Wipers 85-87 into engagement with the calling line which will be assumedto be that comprising conductors 9l'and 92 extending from substation T and terminating on contacts 88 and 89. The connector signals the called station in the well-known manner, and when the called subscriber answers reverses battery back over the trunk in theusual maner '2'"1" Txllfterdialing the digits of thewanted stat-ion ,the attendant willre store key Kto normail or joperate it to the left. 1 The calling de vice is then disconnected from the trunk the releasetrunkgrelay 71 will remain locked and "the holding circuit forthe line switch llll) that: the twe windings-oppose e'ach'other. henzthezcalled station answer-mthegconnectorreversesz battery as previouslymentioned, and, theacurrent fi'ow being reversedin the lower windingz'oi'. polarized: relay 12, the two windings assist eachother and relay 1-2;.operates. I Relay 12 closes a holdingcircuit for the upper Winding of relay, 13. atjarmat'ure 15.. The attendant will normally'throw key K Lethe-left and. listen in on the trunk mtil the called party answers or, if there are other calls 'toheattendedto, key K may be'restored to normal andv the otherv calls attended. to. When the attendant is-assuredrthat the called station. has answeredreceiver RE may be replaced on-the switch-hook, whereupon the circuitof relay 32; will beopened and that relay deenergized, Relay 32 at armature 35 opens theholdingcircuit for the lower winding of relay 1-3, which, however, remains locked up over its u'pper-windingiunder control: of relay 12; At thetermination of the call the-subscriber at substation 'I will replace thereceiver, thereby opening the called line loop. Connect-or G will reverse battery over the trunk back tonormal and: relay 1:2 will deenergize, andopenthe: circuit of relay 13; Relay 13 will then deenergizeandopen the holding loop to the line switch, thus releasing the-line; switch, and the connector-in.

the usual" manner. The equipment in the P. will restore-to; normal and will be immediately availablefor another-call. The central oflice: subscriber or operator is thus unable to hold up the connection in the P. A. It will be noted that theRjA. X.

equipment will not releaseuntil the attend ants receiveris replaced onthe switch-hook.

In the, foregoing description it was assumed that the-call was extended from'a common battery'manual central oflice. It is obvious that similarcalls maybeextended from .magneto'manual central oflices 01"f10111'5tl1l0 matic central offices, the only requirement being that ringing current be projected on.

i is considered new a'udfis desired tohave pro tected will be pointed out in the appended claims;

' What is claimed is: r

1,. In a telephone system, an incoming trunk, at attendants position, means for extending a call oversaid trunkto said position,

automatic switches, means controlled bythe attendant for further extending the call oven said switches, means controlled by the attendant for maintainingsaid switches in operated position, and means operative responsive to the-call being answered for maintaining said switches in operated position independent of said; attendant controlled means. 2. In an automatic telephone system of the type in which incoming calls are intercepted by an attendant, means controlled by the attendant for further extending a callover the regular exchange equipment to a called station, andmeans efiective when the callis an.-

sweredior transferring control of the release of the connection to the called station.

3. In a telephone system, an incoming trunk, a relay having two inductively coupled windings one of which. is, bridged across the conductors of the trunk, a locking circuit for said relay including the other winding, means for operating the relayresponsive to the: extension of a call over the trunk, means for closing said lockingcircuit responsive to the operation of the relay, and means for im pressing a characteristic tone on said trunkl via said locking circuit and the inductively coupled windings of said relay.

4. Ina telephone system, a two-conductor trunk line, a double wound relay having onev winding bridged across the conductors of said trunk. line, a locking circuit for the relay in cludingthe other winding thereof, and means for intermittently connecting a tone source to said locking circuit whereby a tone is tin-'- ductivelyapplied to the trunk line;

5. In a telephone system, a two-conductorv trunk line, a double wound relay having one winding bridged acrosstheconductors of said trunk line, means controlled over thetrunk line for operating-said. relay, 3. second relay, means controlled by said first relay for completing. a holding circuit for its other winding and said second relay in series, and means controlled by'said second relay for intermittently connecting a source of tone to said I holding circuit. I

6. In a telephone system, a two-conductor trunk line terminating in an operators position, a doublewound relay having one winding bridged across the conductors of the trunk line, a signal at said position connected in parallel with the other winding of said relay, means for operating said relay responsive to the extension of a call over the trunk line, means controlled by said relay for completin g a circuit for its other winding and for said signal, means-for intermittently connecttone is intermittent-1y applied to the trunk line, means for answering thecall, and means responsive to theanswering of the call for opening said circuit tov disable said signaland to disconnect said tone source.

7. In a telephone system, a trunk line extending through an attendants position to an automatic switch, a telephone set atthe posiion rendered effective responsive tothe removal of the receiver from the switch-hook, means for connecting saidset to the trunk line to answer a callthereon, means controlled by; the attendant for operatingsaid switch to;

mg a source of tone'to said circuit whereby a) further extend the call to a called subscriber,

and arrangements whereby the attendant is required to keep the receiver off the switchhook until the called subscriber answers in order to prevent the release of said switch. 

